The invention relates to a joint between the ends of two flexible ventilating ducts, of which an end of one of the ducts has a stiffening ring and is telescoped over the other duct, an outer capping connected to said other tube enclosing the joint between the telescoped ducts.
When drilling tunnels, fans are used which through a system of flexible ducts or pipes blow fresh air into the interior of the tunnel and likewise blow air out of the tunnel. As the drilling gradually advances and the tunnel becomes longer, new ducts or pipe sections must be connected to each other.
When connecting the ducts, it is presently common to use a system, in which the ducts are provided at one end with a stiff ring of steel. The ring of steel has the same outer diameter as the duct and is placed at the outlet end of the duct. When connecting two duct sections, the new duct is brought a certain distance past the ring of steel at its outside, after which a clamping ring is provided and tightened over the ring of steel according to the principle of a hose clamp. However, this system often has the drawback of being time consuming and difficult when forcing the new duct over the ring of steel. Furthermore, there is a certain air leakage at the clamping ring, and the position of the joint is not fixed. Moreover, the stiff ring takes up a lot of space during transport.
Another way of connecting ducts is by means of zippers, zipper holes being provided at the ends of the ducts. When connecting two ducts, co-operating ends of the ducts are connected and the zipper is connected in a usual way by means of a runner. Generally, the zipper halves are sewed onto the duct resulting in the seam forming a source of air leakage. In order to reduce the air leakage at the joint, sealing tabs are often provided internally and externally of the duct. The drawback of this connecting system is that it is not completely sealed, and especially when reversing the air flow, possible sealing tabs are blown backwards exposing the joint and creating an air leakage so big that reversing of the airflow is not possible due to leaking explosion gases. Furthermore, when connecting ducts by means of zippers, it is neither possible to adjust the ventilating ducts vertically and laterally nor to make elbows on the duct. Moreover, connection of ducts by using zippers of different fabrications is not possible due to different types and different positions for the zipper halves.
Generally, the material for the duct or pipe is a polymer material, for example a PVC-coated polyamide or polyester fabric, which is sufficiently elastic when being forced over said ring of steel. The drawback of this elasticity is that it also gives rise to an expansion of the duct material due to the air pressure formed in the duct during use, leading to a creation of obstacles for the air flow by the formation of waists at the joints, for rings of steel as well as zippers. As a result, whirls are created and the flow is reduced. As compensation, the fan capacity has to be increased with higher energy costs as a result.
The object of the invention is to accomplish a joint when connecting two flexible ventilating ducts by which a straight and undisturbed air flow is achieved. The object of the invention is also to produce a joint by which the above-mentioned drawbacks are eliminated.
According to the invention this object is achieved by a joint between the ends of two flexible ventilating ducts, of which an end of one of the ducts has a stiffening ring and is telescoped over the other duct. The joint also has an outer capping connected to the other duct enclosing the joint between the telescoped ducts. The outer capping is externally attached to the other duct inside its end and extends axially from the attachment point over said one duct. An outer clamping ring, which encloses the ducts in the area of the stiffening ring, at an edge bulge of the capping is kept in sealing engagement against said one duct inside the-stiffening ring.
Other advantageous detail designs of the joint are disclosed herein.
The capping is provided with a surrounding edge bulge and is here kept pressed against said one duct. A flexible cord or cable may be provided in the bulge. Preferably, the cord is made of a plaited or laid synthetic fibre material or a plaited cotton rope. The cable is preferably made of metal.
At the area of the stiffening ring said one duct has an inner diameter, which is somewhat larger than the outer diameter of said other duct. The capping has an inner diameter, which is somewhat larger than the outer diameter of said other duct but somewhat smaller than the outer diameter in the area of the stiffening ring.
An end portion of said one duct diverges slightly outwards, and an end portion of said one duct is folded over the stiffening ring and is internally or externally welded to the duct.
Preferably, the duct material is a PVC-coated knitted polyester reinforcement having insignificant or low elasticity. The capping is on the other hand preferably made of a PVC-coated polyamide or polyester fabric having a larger elasticity than that of the duct material.
Owing to the joint according to the invention, a connection of two flexible ventilating ducts is accomplished, by which a straight and undisturbed flow of air is achieved. The joint does not constitute any hindrance for the airflow, and therefore a lower fan capacity can be used resulting in lower energy consumption. Moreover, a completely sealed joining of ducts w with essentially non-existent air leakage is achieved. Two kinds of sealings are achieved with the invention. The first sealing is achieved by the bulge bearing on the stiffening ring when it is pressed together with the clamping ring, and the other sealing is achieved by the other duct bearing on the joint as the air flow presses it against the inside of the joint.
The ventilating ducts at the joint according to the invention are adjustable vertically and laterally and also have a firmly fixed joining position. Moreover, the flexible ducts with their flexible stiffening rings are very easy to install and advantageous during transports.